1. Field of the Invention
The invention relates to an ignition plug for use in the internal combustion engines of automobiles and the like, and a process for instantaneously igniting the gas mixture in a combustion chamber thereof.
2. Background Art
So far, as disclosed in Japanese Published Patent Application No. 62-11471, an art to accelerate the ignition propagation of gas mixture in a combustion chamber in the early stage of ignition was developed by the present inventors, in which an ignition groove was provided on the piston side of a ground electrode in order that the gas mixture in the small cavity of the ignition groove may be ignited as early as possible To be more exact, in the art, the end of the ignition groove is open toward a cylindrical center electrode with a spark gap put in between, so that ignition seeds that appear in the spark gap radially bounce on the center electrode and only a few of them can effectively ignite the gas mixture in the ignition groove. Thus, the problem is that with the ignition plug, the time from the appearance of ignition seeds to the combustion of gas mixture in the ignition groove cannot be reduced any more. The situation being such that, as shown in Japanese Published Patent Application No. 62-321045, an ignition groove was provided to on the top of a center electrode, and a ground electrode was opposed to the ignition groove in such a way as to cover it up against a piston placed ahead of the center electrode. With this improvement, the time to ignite gas mixture in the ignition groove was certainly able to be reduced as anticipated; however, since the ground electrode and the ignition groove are put parallel to each other, ignition seeds have to travel as much as the length of the ignition groove is increased to ignite the gas mixture at the end of the ignition groove. Contrary to this, it is unavoidable that the capacity of the ignition groove to hold the gas mixture lessens as much as the length thereof is reduced.